Decreases in case-fatality and mortality rates for invasive pneumococcal disease in Olmsted County, Minnesota, during 1995-2007: a population-based study.
BACKGROUND
Following the introduction of a 7-valent pneumococcal conjugate vaccine for children in 2000, there has been a decrease in the incidence of invasive pneumococcal disease among both children and adults in the United States. We evaluated the hypothesis that the case-fatality and mortality rates for invasive pneumococcal disease have also decreased since 2000.


METHODS
We conducted a population-based outcome study in Olmsted County, Minnesota, during the period 1995-2007 that involved patients of all ages.


RESULTS
From 1 January 1995 through 31 December 2007, a total of 180 eligible cases of invasive pneumococcal disease were identified in Olmsted County. During the 13-year study period, the overall case-fatality rate for invasive pneumococcal disease decreased from 19% (14 of 74 cases) in 1995-1999 to 5% (5 of 91 cases) in 2001-2007, an 83% decrease, after adjustment for age, sex, and Charlson comorbidity index score (P =.003). The largest decreases in case-fatality rate were seen among adults aged >/=65 years (an 86% decrease, from 31% [9 of 29 cases] to 8% [3 of 40 cases]; P=.02) and patients with invasive pneumonia (a 78% decrease, from 22% [12 of 55 cases] to 7% [5 of 72 cases]; P=.01). The overall mortality rate for invasive pneumococcal disease decreased from 2.9 deaths per 100,000 person-years in 1995-1999 to 0.7 deaths per 100,000 person-years in 2001-2007, a 78% decrease, after adjustment for age and sex in a Poisson regression model (P=.002).


CONCLUSIONS
Significant decreases in the case-fatality and mortality rates for invasive pneumococcal disease were demonstrated in the population of Olmsted County. Additional studies are needed to confirm our findings in other populations.
Tsigrelis
Constantine
C
Department of Medicine, Division of Infectious Diseases, Mayo Clinic, Rochester, Minnesota, USA.
Tleyjeh
Imad M
IM
Lahr
Brian D
BD
Nyre
Lisa M
LM
Virk
Abinash
A
Baddour
Larry M
LM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000401:mortality*; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000401:mortality*